This gets to the loot vapor-lock problem of another thread. It's hard to optimize when it seems like every slot can have just about every stat. I would be all for stats in general being more focused, so that you know when you look at one system you're only going to see some specific stats, which thus makes it easier to compare loot. I'd be all for trap skills just going on certain slots, in the greater context of making all skills only found in certain slots.
Bear in mind that it's not true that just about every stat can go on every slot:
+Attack (not the +% one) is only for weapons
+Range is only for weapons
+Ammo is only for weapons
+Splash is only for weapons
+Shields can cross-over
+Regen can cross-over
+DR can cross-over
+%Attack can cross-over
+%Shields can cross-over
+%Propulsion can cross-over
+%Computer can cross-over
+%PowerGen can cross-over
+Stealth is only for propulsion
+Overload is only for propulsion
+TrapSkill can cross-over
+Sensors can cross-over
+Hacking is only for computers
+Virus is only for computers
+Sentries is only for computers
+Mines is only for computers
-PowerCostForRestOfSystem can cross-over
So of a grand total of 21 stats, 11 can cross-over and 10 cannot.
I certainly could make them all just never cross over, but that's going to MASSIVELY cut down on the variety of parts. In fact I'll probably have to take out the extra effect from part "variants" (the ones that use a somewhat different image than the "base" type of the part) just because there won't be that many distinct effect types to go around.
And if we just reduce the number of cross-over stats (say, taking +%Propulsion and +TrapSkill out of the pool) that's going to make the others way more common overall.
So I actually don't mind removing the cross-over thing at all, and change this from being a sort of Torchlight-esque affair to something where the idea is that the parts are just fairly simple (more like bits of circuitry than enchanted vorpal broadswords), but I'm not sure if that's what folks actually want here.